Create a Drillthrough Report in SSRS

Create a new Report Server Project or open an existing one.

Design your main report with the summary data you want to display.

Identify the data element (textbox, chart, tablix cell, etc.) that the user will click on to trigger the drill-through action.

Assign an action to that element by right-clicking it and selecting "Textbox Properties" (or appropriate property for your element).

In the "Textbox Properties" dialog, go to the "Action" tab.
Choose "Go to report" as the action type.
Select the sub-report you want to display when the user clicks on the element. If it's not already created, you need to create the sub-report separately.
Define any parameters that need to be passed to the sub-report. These parameters often represent the context from the main report, such as the ID of the selected item.

Create a new report in your project, which will serve as the sub-report.
Design the sub-report to display the detailed information you want to show.
If you're using parameters from the main report, make sure the sub-report can accept those parameters.

Run the main report in preview mode.
Click on the element you defined as the drill-through action.
The sub-report should open with the relevant data.
Deploy and Configure:

Deploy your reports to the SSRS server if you haven't already.
Make sure that the necessary permissions are set for the users to access both the main report and the sub-report.
Test on the SSRS Server:

Access the report through the SSRS web portal or your application.
Click on the elements in the main report to test the drill-through functionality.

Remember to handle any error cases, such as when the user clicks on an element that has no related data in the sub-report. You can add handling logic in the sub-report to display a message or handle such cases gracefully.

This is a basic outline of how to create a drill-through report in SSRS. You can make your reports as complex as needed to meet your specific requirements.